a. Field of the Invention PA1 b. Description of the Related Art
The invention relates to a regenerative brake controller which is mounted on a motor vehicle such as an electric vehicle or an electric locomotive.
Drivers use engine braking which stops an internal combustion engine vehicle by the pumping work and friction torque of the internal combustion engine. In some types of motor type vehicles there is a function of controlling the regenerative braking torque so that the engine braking torque is simulated by the regenerative braking torque, in order to make the drive feeling similar to that of an internal combustion engine vehicle (see, e.g., Japanese Patent Laid-Open Publication No. Sho 51-125819). The engine braking torque of the internal combustion engine vehicle is determined according to the pumping work and friction torque of the internal combustion engine and, therefore it is substantially constant except for when the number of revolutions of the internal combustion engine is low. In order to give the driver a feeling similar to that of the internal combustion engine vehicle, in the above-mentioned motor type vehicle, the regenerative braking torque is controlled so as to simulate the engine braking torque to keep it at a substantially constant level.
However, even when the braking torque is identical, its effect is varied when a vehicle running resistance or vehicle conditions are changed. For example, when the vehicle's load, such as total weight of cargo and passengers is varied, or when a road gradient is varied, the effect of engine braking varies. Therefore, in a conventional vehicle, to deal with the change in the vehicle running resistance, when making use of the engine braking, the driver is often required to further depress the brake pedal or operate the shift lever to a lower gear. When the frequency of such operations is increased, the vehicle drivability deteriorates.
Besides, in the conventional vehicle, the driver has no influence on the engine braking effect except for the operation of the shift lever. Thus, when the driver is requesting generation of a large braking torque before depressing the brake pedal, e.g., when the accelerator pedal is quickly released and the brake pedal is then depressed, the engine braking effect is only at a level corresponding to where the shift lever was positioned immediately after the accelerator pedal is released, and such a low effect is a problem in the conventional motor type vehicle.